then fabricated into the shapes needed in the early
were supposed to have been carried out in dry
atomic bombs.
the welded steel bomb was difficult to saw op
Before plutonium became available in quanti-
such a confined space.
On at least two occas
ties, preliminary experiments were carried out using
certain procedures were carried out in the op:
uranium and other metallic "stand-ins."
laboratory.
The opera-
On one of these occasions, the mn
tors soon learned that reduction of plutonium and
count of one operator was 11,900 counts per m
other metallic halides with alkali or alkaline earth
and the laboratory in which the work was carr:
metals was relatively easy but that, when operating
on was heavily contaminated.
on a small scale, the reduced metal tended to remain
his assistant both have measurable body burder
mixed with the cindery slag rather than to form well
plutonium.
consolidated "buttons."
(Since the melting point of
This metallurgi:
In September 1944, thi
method was discontinued in favor of the "stati
plutonium was unknown at this time, the reaction
bomb"
vessels were considerably overheated, causing reac-
where it was easier, quicker, and gave better
tions with the refractories.)
sults than the centrifugal method.
were
While experiments
carried out to enable plutonium buttons
we
method, which had been developed to the
The principle employed in the stationary
to be
produced on a larger scale in stationary bombs, the
method was to pack a mixture af PuF, and metal
separation of plutonium from the slag was first
calcium in refractory liners made of electrica
successfully achieved by the use of centrifugal
fused MgO contained in argon-filled steel bomb
force to throw the molten metal into the tip of a
On heating the bomb a strongly exothermic/ther
cone-shaped container.
This was called the "cen-
reduction reaction occurred, and the plutonium
trifugal bomb" method.
PuCl, or PuF,, mixed with
separated clearly from the fluid CaF,
lithium in a refractory cone-shaped beryllium oxide
2
slag.
A
tion of iodine to the charge helped ignition a
liner, was placed in an atmosphere of argon in a
improved collection efficiency.
steel bomb about 1 in. in diameter and 1-1/2 in. in
standard method of reducing plutonium during t:
height.
war.
This was welded shut and placed in an ali-
This became t!
All loading and unloading operations wer
graphite centrifuge, heated electrically to 1100°C
ried out in dryboxes.
while being rotated.
on, disassembly of the bomb was easier than in
soon obtained.
Good cohesive buttons were
The first 500~-mg metallic button of
Because the lid was bol:
case of the welded bomb.
Moreover, the well fi
almost pure plutonium? was made by this method on
reaction products were less dusty than those ir
May 26, 1944 (Fig. 7).
earlier small-scale experiments.
Although loading and unloading of the bombs
Nevertheless,
metallurgist who developed this method does hav
measurable bedy burden of plutonium.
IV.
EXPOSURE OF THE SUBJECTS
By March 1945, thé plutonium urinary assay
6
method had been developed to the point where i:
could be applied to the plutonium workers.
The
assay system had to be extremely Sensitive, as «
RRAKEREREKKEKE
.
.
The contamination occurred during p
aration of the metallic button mentioned above.
Unbeknown to their supervisors, these workers bi
the reduction at midnight.
Fig. 7.
A 500-mg metallic button of almost pure
plutonium.
10
The next morning thi
plutonium button in an appropriate container wa:
allegedly found on the desk of Dr. Cyril Smith,
Associate Leader of CMR Division, and extensive
contamination had occurred throughout the labor:
and adjacent hallways. The workers were nowher¢
around but were finally located in the bar of tl
La Fonda Hotel in Santa Fe, where they were cele
brating their success in reducing plutonium by :
technique they had developed.